Autonomous cruise control (ACC; also called adaptive cruise control or radar cruise control) is an optional cruise control system for roadvehicles that automatically adjusts the vehicle speed to maintain a safe distance from vehicles ahead. It makes no use of satellite or roadside infrastructures nor of any cooperative support from other vehicles. Hence control is imposed based on sensor information from on-boardsensors only. Cooperative Adaptive Cruise Control (CACC) further extends the automation of navigation by using information gathered from fixed infrastructure such as satellites and roadside beacons, or mobile infrastructure such as reflectors or transmitters on the back of other vehicles.[citation needed]

Such systems go under many different trade names according to the manufacturer. These systems use either a radar or laser sensor setup allowing the vehicle to slow when approaching another vehicle ahead and accelerate again to the preset speed when traffic allows. ACC technology is widely regarded as a key component of any future generations of intelligent cars. The impact is equally on driver safety as on economising capacity of roads by adjusting the distance between vehicles according to the conditions.

Laser-based systems and radar-based systems compete in quality and price.

Laser-based ACC systems do not detect and track vehicles in adverse weather conditions nor do they reliably track extremely dirty (non-reflective) vehicles. Laser-based sensors must be exposed, the sensor (a fairly large black box) is typically found in the lower grille offset to one side of the vehicle.

Radar-based sensors can be hidden behind plastic fascias; however, the fascias may look different from a vehicle without the feature. For example, Mercedes packages the radar behind the upper grille in the center, and behind a solid plastic panel that has painted slats to simulate to the look of the rest of the grille.

Single radar systems are the most common. Systems involving multiple sensors use either two similar hardware sensors like the 2010 Audi A8[1] or the 2010 Volkswagen Touareg,[2] or one central long range radar coupled with two short radar sensors placed on the corners of the vehicle like the BMW 5 and 6 series.[3]

Radar-based ACC often feature a precrash system, which warns the driver and/or provides brake support if there is a high risk of a collision. Also in certain cars it is incorporated with a lane maintaining system which provides power steering assist to reduce steering input burden in corners when the cruise control system is activated.

GPS-aided ACC: the GPS navigation system provides guidance input to the ACC. On the motorway, the car in the front is slowing down, but with turn signal on and it is actually heading for a highway off-ramp. A conventional ACC would sense the car in front was decelerating and it would simply apply brakes accordingly. But with GPS-guided ACC takes into account the approaching highway exit and it simultaneously receives images from a camera attached e.g. behind the front pane to the rearview mirror. The camera may detect the turn signal from the car ahead. So instead of braking, this new system continues uninterrupted, because it knows that the car in front will exit the lane[4]

The next generation, also known as the Cooperative Adaptive Cruise Control, will include information served from a vehicle ahead in the same lane. Such dependant approach however requires standardization across manufacturers and model generations. There is no vision when such agreement could come into practice. All designs without such cooperative support will operate with comparably lower dynamic, but promise better reliability and independent operation.

The cooperative approach is the better advances concept to improve road capacity. Therefore reach of detection must exceed the capabilities of on-board laser or radar. A wireless communication between vehicles in a queue may not aid braking, but can be used for adjusting speed to avoid longitudinal oscillations.

1992: Mitsubishi was the first automaker to offer a Lidar-based distance detection system on the Japanese market Debonair. Marketed as Distance Warning, this early system only warned the driver, without influencing throttle, brakes or gearshifting.[5][6]

1995: Mitsubishi Diamante introduced laserPreview Distance Control. This early system only controlled speed through throttle control and downshifting, but did not apply the brakes.[5]

1997: Toyota began to offer a "laser adaptive cruise control" (lidar) system on the Japanese market Celsior.[7] It only controlled speed through throttle control and downshifting, but did not apply the brakes.

2004: Toyota added "low-speed tracking mode" to the radar ACC on the Crown Majesta.[7] The low-speed speed tracking mode was a second mode that would warn the driver if the car ahead stopped and provide braking; it could stop the car but then deactivated.[19]

2005: In the United States, Acura first introduced radar Adaptive Cruise Control (ACC) integrated with a Collision avoidance system (Collision Mitigation Braking System (CMBS)) in the late calendar year 2005 in the model year 2006 Acura RL as an optional feature.[20]

2005: Mercedes-Benz S-Class (W221) refined the Distronic system to completely halt the car if necessary (now called "Distronic Plus". Now offered on E-Class and most Mercedes sedans. In an episode of Top Gear, Jeremy Clarkson[citation needed] demonstrated the effectiveness of the cruise control system in the S-class by coming to a complete halt from motorway speeds to a round-about and getting out, without touching the pedals.

2006: Audi introduced Full speed range ACC plus on the Audi Q7. It has low-speed mode, and additional functions to warn the driver of a potential collision, and prepare emergency braking as needed.[21] The system supplied by Bosch is also available in the 2008 Audi A8, the Audi Q5, 2009 Audi A6 and the new 2010 Audi A8. The Audi A4 is available with an older version of the ACC that does not stop the car completely.

2006: Nissan introduced Intelligent Cruise Control with DISTANCE CONTROL ASSIST on Nissan Fuga.[22] It pushes the gas pedal against the foot when the DVD navigation with GPS determines that an unsafe speed is being maintained. If the Autonomous cruise control system is being used, the Distance Control Assistance will reduce speed automatically, and will warn the driver that an adjustment is being made with an audible bell sound.

2006: September 2006 Toyota introduced its "all-speed tracking function" for the Lexus LS 460.[7] This radar-assisted system maintains continuous control from speeds of 0 km/h to 100 km/h and is designed to work under repeated starting and stopping situations such as highway traffic congestion.[23]